Securing Your Web Server from Prying Eyes
If you get into the mind of potential hackers to your site, you soon realize that it would be a great benefit for them to know what operating system and web server you are running. With this information, they could exploit weaknesses in the web server that have been documented by Microsoft and BugTraq. This article will show you how to hide the identity of your web site by making some configuration changes to IIS and using URLScan or by installing an ISAPI filter. The code for the ISAPI filter is available, or you can use a commercial available product.
http://www.asp101.com/articles/wayne/pryingeyes/default.asp